But it isn't doing it alone. The company's health team has been working with a tiny start-up called Health Gorilla, according to two people familiar with the initiative.

Sources said that Health Gorilla is specifically working with Apple to add diagnostic data to the iPhone, including blood work, by integrating with hospitals, lab-testing companies such as Quest and LabCorp and imaging centers.

The start-up, which has raised just shy of $5 million in funding, specializes in giving doctors a "complete picture of patient health history," according to its website. CEO Steve Yaskin founded the company after a doctor friend of his was frustrated with the process of transferring patients' diagnostic test results in their practice, according to a blog post from Health Gorilla investor True Ventures.

It is primarily geared to physicians and serves as a marketplace for them to place orders and share medical records. But it also has a free offering for patients, which promises to gather up medical information in 10 minutes.

Both Apple and Health Gorilla's Yaskin declined to comment on the partnership.

Apple is looking to solve a big problem that has plagued the medical sector for decades.

Hospitals often struggle to access vital data about their patients at the point of care, which is spread among third-party labs, primary care groups and specialists. And those knowledge gaps can often lead to missed diagnoses or unnecessary medical errors, numerous studies have found.

Sources told CNBC that Apple is attempting to solve this "interoperability" problem by making the patient the center of their own care. The goal is to give iPhone users the tools to review, store and share their own medical information, including lab results, allergy lists and so on. That's a deviation in strategy from Apple's current health efforts, which have focused on aggregating fitness information like the number of steps taken during the day or hours of sleep.

Apple isn't the first technology giant to jump into the personal health record space: Microsoft has a portal called Health Vault, while Google had a project called Google Health which shut down in 2011.